Basically, you take an append _t to the directory, convert the period in the file name to an underscore and append .JPG. Here are a few examples:
|Image URL||Thumbnail URL|
Using a _w instead of a _t seems to give a slightly larger image. This might be useful for hover over events.
I wisht to have a list that contains details about an item including a thumbnail of the picture attached to that item.
How can I create thumbnails of attached pictures?
I don’t know that this is possible. The functionality is actually implemented on the picture library. You could investigate adding the fields you want to a picture library and make the item the picture library itself.